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https://issues.apache.org/jira/browse/HDFS-5583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13906104#comment-13906104
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Kihwal Lee commented on HDFS-5583:
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Thanks for the review, Brandon.
- The admin wants to know whether the command was received: This is determined
by the return code of the command. As with other commands, when the return code
is not 0, the state is non-deterministic and only then the command may be
reissued. I do not believe that this is a common case. Moreover, the shutdown
normally take less than two seconds and probably the reissuing shutdown
manually take more than that. In my opinion, adding support for reporting
progress won't have much value. If you still feel that it needs to be changed,
I will change it. Please let me know what you think.
- I am planning on adding at least one more OOB ack type in near future for
write draining, which will be useful for decommissioining. The reserved enums
make certain checks more efficient.
I will address the rest of the comments when you finish the review.
> Make DN send an OOB Ack on shutdown before restaring
> ----------------------------------------------------
>
> Key: HDFS-5583
> URL: https://issues.apache.org/jira/browse/HDFS-5583
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Attachments: HDFS-5583.patch, HDFS-5583.patch, HDFS-5583.patch
>
>
> Add an ability for data nodes to send an OOB response in order to indicate an
> upcoming upgrade-restart. Client should ignore the pipeline error from the
> node for a configured amount of time and try reconstruct the pipeline without
> excluding the restarted node. If the node does not come back in time,
> regular pipeline recovery should happen.
> This feature is useful for the applications with a need to keep blocks local.
> If the upgrade-restart is fast, the wait is preferable to losing locality.
> It could also be used in general instead of the draining-writer strategy.
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